For convenience purposes, it is well known to provide garage doors which utilize a motor to provide opening and closing movements of the door. Motors may also be coupled with other types of movable barriers such as gates, windows, retractable overhangs and the like. An operator is employed to control the motor and related functions with respect to the door. The operator receives command signals for the purpose of opening and closing the door from a wireless remote, from a wired or wireless wall station or other similar device. It is also known to provide safety devices that are connected to the operator for the purpose of detecting an obstruction so that the operator may then take corrective action with the motor to avoid entrapment of the obstruction.
How safety devices are used with a door operator system have evolved from the days of no uniform standard to the currently applied government regulations as embodied in Underwriters Laboratories Standard 325. UL Standard 325 encompasses safety standards for a variety of movable barriers such as gates, draperies, louvers, windows and doors. The standard specifically covers vehicular gate or door operators intended for use with garages and/or parking areas. Such devices require a primary safety system and a secondary safety system which are independent of each other. Primary entrapment systems sense the operator motor's current draw or motor speed and take the appropriate corrective action if the monitored value is exceeded. Primary systems must be internal within the operator head. Secondary entrapment systems are typically external from the operator head and may include a non-contact or contact type sensor. But, secondary systems may also be internal to the operator head as long as they are independent of the primary system.
One of the more widely used secondary entrapment, non-contact devices is a photo-electric eye which projects an infrared light beam across the door's travel path. If the light beam is interrupted during closure of the door, the operator stops and reverses the travel of the door. Regardless of how the safety devices work, their purpose is to ensure that individuals, especially children, are not entrapped by a closing door. The photo eyes consist of an “emitter” unit and a “receiver” unit. The emitter emits an infrared (IR) signal that the receiver receives. Upon receiving the IR signal, the receiver responds back to the operator. As shown in FIGS. 1A and 1B, the typical photo eye systems use a 2 wire connection system. Each photo eye set, the emitter and the receiver, has two wires. One wire is identified as the “+” (plus) wire, and the other wire is identified as the “−” (minus) wire. The plus wire is both the power source, typically 10 VDC to 35 VDC, and the signal wire, while the minus wire is the DC ‘ground’ reference wire. The emitter is connected to a power source, preferably in the operator power head, by a wire-1A that includes the plus wire and the minus wire. In a similar manner, the receiver is connected to the operator power head by a wire-1B that also includes a plus wire and a minus wire.
Referring now to FIG. 1C, it can be seen that the receiver, upon detecting an IR signal generated by the emitter can “pull” the power/signal plus wire to a low voltage level close to DC ground. The operator power head detects the power/signal line being pulled low by the receiver and interprets this as a successful IR signal transmission between the emitter and receiver. If the IR signal is interrupted as the door moves downwardly—the power/signal line is not pulled low—then the operator power head takes corrective action and at least stops movement of the barrier.
UL 325 requires that the photo eye system be installed to detect a 6 inch high object. Thus the photo eyes are typically installed at a height of 4 inches to 6 inches above the garage floor. At this height, the IR beam will be interrupted by a small child lying on the floor, which is under the door's path of travel. But, one issue consumers have with this arrangement is that the IR beam can shoot under a vehicle if it is parked only half-way into the garage. For example, many people park their vehicle half-way in the garage during service repair to the engine so as to allow more room for the person to maneuver in front of the vehicle. The IR beam shoots behind the front tires, in front of the rear tires and under the vehicle's frame, missing the vehicle completely. If a vehicle is parked in this position and then a person commands the door to close, the operator closes the door and the door strikes the top surface of the car. The operator then detects the car's presence by its primary inherent entrapment protection system and reverses the door's direction thereby opening the door to its fully-open position. But the door striking the vehicle can cause damage to the vehicle's surface. Therefore, some users of garage door operators mount the photo eyes at a height greater than 6 inches in an attempt to detect a vehicle parked half-way into the garage. But, mounting the photo eyes greater than 6 inches off of the floor creates a hazard since the photo eyes are unable to detect a child laying on the floor.
Several patents disclose various safety and photo-eye configurations, but none appear to directly address the problem of photo-eye height adjustment undertaken by the end user. For example, U.S. Pat. No. 4,922,168 to Waggamon, et al. discloses a safety system with universal attachment to existing garage door openers. A transmitter of infrared energy transmits a beam laterally of the door opening to detect any obstruction to door closing movement. A safety control circuit is adapted for connection to the main control circuit of the existing garage door opener. The existing push button switch is disconnected from the main control circuit and connected to the new safety control circuit. A flexible cable or cord is connected for actual movement in accordance with movement of the door and is connected to the safety control circuit at a reel on which the cord is wound. And the safety control circuit determines if there is actual door movement and actual door closing movement, as well as being responsive to an obstruction to door closing movement to apply a signal to stop the door and then apply another signal to start the door in its opening movement.
U.S. Pat. No. 5,285,136 to Duhame discloses an automatic door operator with a continuously monitored supplemental obstruction detector. In a first embodiment, the obstruction detector is a radiant beam obstruction detector that transmits a beam of modulated radiant energy across the door opening. A safety signal generator produces an active safety signal only on unobstructed receipt of radiant energy by a receiver. Failure to receive the active safety signal when the motor is closing the door at least stops the door. A two wire cable, which carries both power and the active safety signal, connects the supplemental obstruction detector to the automatic door operator. Constant activation of a portable transmitter or of a local push button can override the supplemental obstruction detector to close the door. An alternative supplemental obstruction detector includes a safety edge having a compressible tube disposed on a leading end of the door. Plural conductors change their conductive state upon compression of the compressible tube. An oscillator sealed within the tube at one end supplies the safety signal. This embodiment may include a delay upon detection of compression of the compressible tube so that contact with the floor is not detected as an obstruction.
U.S. Pat. No. 5,286,967 to Bates a modulated light beam obstacle detector for use as a safety mechanism in an automatic closure operator which must operate in varying ambient light conditions. If the obstacle detector senses the interruption of the light beam, the motion of the door is arrested or reversed. The obstacle detector uses an auxiliary light source connected in a feedback circuit to maintain a constant background illumination on the light detector and thereby hold the light detector in conduction at all times. In this manner, the presence of the light beam can be sensed regardless of the ambient light conditions.
U.S. Pat. No. 5,428,923 to Waggamon discloses that a light beam in an obstruction detector is coded into packets of pulses by a transmitter according to a code generated only by the transmitter. When the light beam is received, the receiver recovers the code signal and supplies it to a code detection circuit. In one preferred embodiment, to detect the code, the code detection circuit supplies the code signal and a delayed version of the code signal to an “exclusive or” gate. In another embodiment, a frequency detection circuit determines whether the code signal detected by the receiver is within a predetermined permissible range. If the code is not present, the door operator system reverses the door if it is closing, and prevents the door from closing if it already is in the up position, or if it is opening. The door operator system will operate in this way not only in response to obstructions, but also, in response to errors and malfunctions in the wiring to the transmitter and receiver, and in the transmitter and receiver themselves.
U.S. Pat. No. 5,465,033 to Fassih-Nia discloses a safety system which comprises a light beam transmitter and receiver and means connected through a standard AC power plug to the main power supply of an automatic garage door opener for controlling the power thereto. The transmitter transmits a beam of light across the opening of a garage door. The receiver is positioned to receive the light beam if there is nothing obstructing the beam. The receiver generates a signal indicating when the beam is being received. The means disconnects the power to the garage door opener when a signal is generated indicating that the light beam is not being received. The garage door is thus prevented from making contact with and hurting or damaging a person or object in its path.
U.S. Pat. No. 5,584,145 to Teich discloses a wireless safety system for a garage door opener adapted for use at least in part with an independent energy source. The wireless safety system includes a control circuit for controlling movement of the garage door. An activation member provides an input to the control circuit to initiate motion of the garage door. A detecting member detects whether an obstruction is present in the path of the garage door. The detecting member includes a first state, wherein the detection member does not detect obstructions and consumes minimal energy, and a second state wherein the detection member detects obstructions. The detection member is selectively switchable between the first state (dormant) and the second state (active) by the control circuit.
U.S. Pat. No. 5,656,900 to Michel, et al. discloses a garage door operator has an electric motor controlled by a control unit. A transmission is connected to the motor to be driven thereby to open and close a garage door. An infrared obstacle detector is connected to the control unit and includes a unitary infrared pulse emitter and an infrared detector. A missing pulse detector is coupled to the infrared detector to generate a door opening signal if the door is closing when the pulses are absent due to the infrared being interrupted by an obstacle or not having been generated. The control unit receives the door opening signal and causes the electric motor to open the garage door.
As will be appreciated from a review of the above patents, none appreciate the problem associated with the end-user surreptitiously moving the photo-eye set from the intended location. Therefore, there is a need in the art to further improve the safety features provided by a photo-eye system.